test: add check for root user

Currently this test fails if run as the root user:
Mismatched innerFn function calls. Expected exactly 62, actual 42.

The motivation for this is that when building node in a docker
container it is convenient to be able to build as root.

PR-URL: #19850
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>

test/parallel/test-child-process-spawnsync-validation-errors.js

@@ -3,18 +3,11 @@ const common = require('../common');
 const assert = require('assert');
 const spawnSync = require('child_process').spawnSync;
 const signals = process.binding('constants').os.signals;
+const rootUser = common.isWindows ? false : process.getuid() === 0;
 
-let invalidArgTypeError;
-let invalidArgTypeErrorCount = 62;
-
-if (common.isWindows) {
-  invalidArgTypeError =
-    common.expectsError({ code: 'ERR_INVALID_ARG_TYPE', type: TypeError }, 42);
-} else {
-  invalidArgTypeError =
-    common.expectsError({ code: 'ERR_INVALID_ARG_TYPE', type: TypeError },
-                        invalidArgTypeErrorCount);
-}
+const invalidArgTypeError = common.expectsError(
+  { code: 'ERR_INVALID_ARG_TYPE', type: TypeError },
+  common.isWindows || rootUser ? 42 : 62);
 
 const invalidRangeError =
   common.expectsError({ code: 'ERR_OUT_OF_RANGE', type: RangeError }, 20);
@@ -64,7 +57,7 @@ function fail(option, value, message) {
 if (!common.isWindows) {
   {
     // Validate the uid option
-    if (process.getuid() !== 0) {
+    if (!rootUser) {
       pass('uid', undefined);
       pass('uid', null);
       pass('uid', process.getuid());
@@ -78,9 +71,6 @@ if (!common.isWindows) {
       fail('uid', Infinity, invalidArgTypeError);
       fail('uid', 3.1, invalidArgTypeError);
       fail('uid', -3.1, invalidArgTypeError);
-    } else {
-      // Decrement invalidArgTypeErrorCount if validation isn't possible
-      invalidArgTypeErrorCount -= 10;
     }
   }
 
@@ -100,9 +90,6 @@ if (!common.isWindows) {
       fail('gid', Infinity, invalidArgTypeError);
       fail('gid', 3.1, invalidArgTypeError);
       fail('gid', -3.1, invalidArgTypeError);
-    } else {
-      // Decrement invalidArgTypeErrorCount if validation isn't possible
-      invalidArgTypeErrorCount -= 10;
     }
   }
 }